摘要:

AbstractThe epitactic behavior of a single chain of polyoxymethylene and of polythiomethylene on alkali halide substrates has been simulated by computing the coulombic, induced dipolar, and dispersion–repulsive potential energies as a function of polymer–substrate geometry. Inspection of the total potential energy surface for a polyoxymethylene chain in a 9/5 helix reveals a favorable alignment in which the chain is parallel to the substrate surface ((001) cleavage plane) with specific positioning along rows of positive charge. This preferential orientation has been found to be independent of lattice matching between the substrate and deposited phase. An identical mode of orientation is predicted for a polyoxymethylene chain and a polythiomethylene chain, both in the 2/1cis‐planar conformation. The theoretical results for polyoxymethylene are in agreement with available experimental evidence, whereas the outcomes of the calculations performed on polythiomethylene should be considered predictive study to be complemented by a future experimental investig

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130411

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractA study has been carried out of the changes in the x‐ray diffraction patterns which occur when oriented fibers or tapes of poly(trimethylene terephthalate) (3GT) and poly‐(tetramethylene terephthalate) (4GT) are subjected to mechanical tensile stress. Although the polymers show very different behavior in detail, in both cases comparatively large reversible lattice strains are observed (∼ several %). The diffraction pattern of 3GT changes monotonically with increasing macroscopic strain, suggesting that the lattice responds immediately to the applied stress, and deforms as though it were a coiled spring. In 4GT, on the other hand, there is no detectable change in the x‐ray diffraction pattern at low macroscopic strains, i.e., low values of the applied stress. At higher stresses, changes in the pattern occur which suggest a definite change in the crystal structure. Finally at the highest values of applied stress, the lattice deformations cease to increase. A preliminary discussion is presented of the relationship of these x‐ray diffraction results to the mechanical stress–stra

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130412

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractFourier transform infrared spectra have been obtained for polyethylene irradiated in oxygen and nitrogen atmospheres. The spectra before and after irradiation have been compared by digital subtraction. The difference spectra are indicative of changes caused by irradiation. Crosslinking and chain scission reactions produce the observed changes.

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130413

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractEPR and matrix ENDOR spectra have been examined for polyenyl radicals in γ‐irradiated PVF, PVF2, PVC, and PMMA polymers. Proton matrix ENDOR is observed for all four polymers, and fluorine matrix ENDOR for PVF and PVF2. By line shape analysis of the ENDOR spectra obtained under comparable conditions, delocalization diameters for the unpaired electron of the polyenyl radical in each polymer are obtained. These diameters indicate extensive delocalization over 5–7 carbon double bonds for the polyenyl radicals investigated. It is suggested that these conjugated and crosslinked radiation products account for the observed nondevelopment of electron beam resist PMMA material at high radiation charge densi

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130414

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractA systematic study of the dispersion curves of the refractive indexes of nylon 6 yarns was made. The parameters were the draw ratio and strain. The measurements show that the dispersions of the refractive indexesn∥andn⊥, parallel and perpendicular to the fiber axis, are equal, independently of draw ratio and strain. The average dispersion equalsnF−nC= 109 × 10−4. Consequently, the birefringence is, within experimental accuracy, independent of the wavelength. The refractive indexes and the birefringence show a change in trend at 10–12% strain. This point corresponds to the yield strain in the stress–strain diagrams. The inference is that beyond the yield point the overall molecular orientation must increase less strongly with strain than before. An analysis shows that the Lorentz–Lorenz relation holds for the average refractive index n̄ = ⅓ (n∥+ 2n⊥). So the change in n̄ versus draw ratio is mainly due to the change in density. By applying the Lorentz–Lorenz relation to the change of n̄ on straining, a value of Poisson's ratio (μ) could be derived. The average value found for nylon 6 yarns was μ = 0.48, which means that the density

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130415

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130416

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130417

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130418

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130419

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130421

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY